1. Field
The present disclosure relates to equipment that can be self-propelled, for example concrete saws.
2. Related Art
In the concrete industry, large slabs of concrete are used to form road beds, building floors and other structures used for its strength and durability. Seams, grooves or other cuts in the concrete may be made in the slabs to form expansion joints, control stress cracks as the slabs cure or to form channels or openings in the slabs to accept other structures. Concrete saws are used to cut the seams, grooves or other openings, and such concrete saws are often very heavy and difficult to move along the concrete slab.
For large or heavy construction applications, heavy self-propelled saws or other large concrete saws are used. Examples of concrete saws and their construction and operation can be found in a number of patents, including U.S. Pat. No. 5,809,985, entitled “Self-Propelled Saw,” U.S. Pat. No. 5,743,247, entitled “Method and Apparatus for Safe Operation of Self-Propelled Concrete Saw,” U.S. Pat. No. 5,680,854, entitled “Self-Propelled Saw,” U.S. Pat. No. 5,477,844, entitled “Slurry Recovery System for a Wet Cutting Saw,” and U.S. Pat. No. 4,664,645 entitled “Blade Drive Shaft Assembly,” all of which are incorporated herein by reference. During setup and operation of the saw, an operator walks behind the saw to control the direction, cutting speed, cutting depth and other operating conditions under which the saw operates. The saw includes one or more wheels allowing the saw to move along the concrete and a frame supported by the wheels on which is mounted a motor or other power supply for operating a saw blade and often for driving one or more wheels to move the saw along the concrete surface. One or more handles extend behind the saw about the level of an operator's hands to allow the operator to manually position the saw. Typically, the saw blade is in the front of the saw and handles extend behind the saw.
For a typical straight cut, the operator aligns the saw blade and often a cutting guide with the intended cutting path. The saw is maneuvered with the saw blade raised above the concrete until the blade and cutting guide are aligned with the cutting path. As the saw blade engages the concrete or other surface to be cut, the blade cuts into the concrete to the desired depth, such as the depth selected by the operator. At the desired depth, the drive wheels are engaged to propel the saw forward to cut the desired slot or groove, which typically follows a straight cut path.
Conventional self-propelled concrete saws have the cutting blade mounted on the left or right side of the machine, so that the saw blade is significantly offset from the center of the machine and supported by the frame of the saw. The drive wheels on the rear axle propel to machine by applying torque and rotation to the drive wheels. When the blade is cutting the work surface, the blade applies an opposite resisting force against the drive from the drive wheels, but the resisting force is off-center to the side of the frame center line. When the wheels propel the saw forward and the blade is down and cutting on the right side of the saw, the saw tends to veer to the right. When the blade is cutting on the left side of the saw, the saw tends to veer to the left.
To compensate for the blade cutting resistance force created by the saw blade, the operator can physically lean on the handle bars to correct for the changing direction away from the cut path. However, such manual correction is not practical for larger saws or where it may be difficult for the operator to maneuver the saw.
On conventional large concrete saws, the rear axle can be manually aligned to extend in a direction other than 90 degrees or perpendicular to the center line of the frame, or in other words the cut path. Re-aligning the rear axle to be other than perpendicular produces a non-parallel propeling force in an attempt to compensate for the blade cutting resistance force produced by the blade while cutting, with the intention of producing a net straight-line movement of the saw along the cut path.
Drive axle re-alignment involves the operator shutting off the saw and using wrenches to loosen the axle mounting bolts. The drive axle is manually adjusted to the desired angle and the mounting bolts re-secured. The saw is then operated with the hope that the adjustment in the drive axle moves the saw in the desired direction. If not, the operator can adjust the drive axle again until the saw moves in the desired direction. However, the amount of blade cutting resistance produced by the blade depends on the depth of cut, the size of the blade, cutting speed, blade age, the concrete hardness, blade configuration and the pavement slope, as well as other conditions. When one or more of those conditions change, the operator may have to stop and re-adjust the axle or try guiding the saw manually.